As a small and growing investor, I'm always looking for higher yield investments, and despite deposits doesn't fit in my wealth building strategy, I have made some pocket money in the past. 

A couple of years ago, while I was still sticking with savings accounts and deposit rates I compared highest deposit rates in Europe, today while browsing for information online about highest deposit rates, I found a lovely website - deposits.org, listing interest rates by countries, regions and even individual banks.

Deposits.org provides the largest marketplace for retail interest bearing products for deposits, personal loans, home loans, credit cards, savings, SME financing and other exotic investment opportunities. We are the one-stop comprehensive reference for international financing and investment

According to the deposits.org research, these following countries offer highest deposit rates in 2018 in national currencies

Country Interest Rate Inflation
Currency
Argentina 20.47% 27.60% ARS
Uzbekistan 20.00% 11% UZS
Ukraine 15.25% 49% UAH
Iran 15.00% 15.30% IRR
Mongolia 15.00% 8.30% MNT
Georgia 10.40% 4.10% GEL
Azerbaijan 10.00% 2.40% AZN
Egypt 10.00% 13.30% EGP
Kazakhstan 10.00% 5.80% KZT
Myanmar 10.00% 8.90% MMK

Data source: World Deposit Rates

Among the highest deposit rates in the World, there are many Former Soviet Union countries (Uzbekistan, Ukraine, Georgia, Azerbaijan, Kazakhstan). As a foreigner living in Georgia, I've been using Georgia's banks in the past for savings, though I have got a very negative experience when dealing with national currencies - they are volatile. My February Savings Report - GEL Loses Another 16.5% Against USD; -17% Against EUR

As you can see in the above table, in some countries inflation rate is far greater than interest rate (Argentina, Ukraine, Iran, Egypt).

I would be cautious when depositing in national currencies.

Now, let's see how about deposits in more stable USD currency:

Country
Interest Rate
Ukraine 5.00%
Cambodia 4.75%
Sri Lanka 3.50%
Zimbabwe 3.50%
Georgia 3.50%
Iraq 3.50%
Laos 3.40%
Azerbaijan 3.00%
Kazakhstan 3.00%
Afghanistan 2.75%

Now, this looks more interesting (despite lower interest rate) - in 2018, you could get up to 5% in deposit rates. On the other hand, countries with highest interest rates are politically and economically unstable, by choosing to deposit at one of the above-listed countries you could actually lose some or all of your savings (in case bank goes bankrupt)

There are plenty of countries in the World with high enough deposit rates in 2018, most of them, on the other hand, are politically and economically unstable and you could risk losing some or all of your money by choosing to invest.

As an expat living in Georgia for more than 7 years, I see it as an option to try deposits in USD currency.