Vanuatu has opened new government bonds option for citizenship by investment with money back after just 2 years (no interest paid). Investors must pay AUD 180,000 to subscribe bond certificate locked for just 24 months. Citizenship is permanent after bonds mature.
Saint Lucia is the another citizenship by investment scheme that offers full money back after 5 years through National government bonds option. All other CBI programs do not issue state bonds. You have to subscribe $300,000 government bonds plus $50,000 government fee. After 5 years the Government of Saint Lucia will pay you back $300,000 back with no interest. Any number of family members can be included without increasing bond sum. The citizenship is permanent even after you dispose off the bonds. Financing these bond is not possible with banks in St.Lucia but it could be possible with the investment bank in your country.
Another option is, you could also invest in real estate $200,000 (buyback shares) offered by five star hotel/resort developers in caribbean. These shares can be kept for 5 years (they do generate 2-4% yields) and can be sold off in the market. The only downside is many developers do not buy back the shares directly, you have to find a suitable buyer yourself which could be a hassle. Titled freehold properties start from $400k or more in the form of luxury villas which can also be sold off in the market with the right price tag.
Donation route could be cheaper if you fall in the $100k budget but it is a non-refundable investment. You make one off donation to state fund in exchange for citizenship.
All in all bond option gives you peace of mind with your invested money. Malta does not offer bonds, while bulgaria and cyprus have downed their shutters offering citizenship for investment.