I can recommend you Runabove, they have 2,5$/mo servers with 2GB supporting Docker.
See this thread for a discussion we had about the service:
https://meta.discourse.org/t/runabove-ovh-experiment-vs-digital-ocean/24428
Shameless Plug for my referral link 
which grants you 10$ credit, so you can use the 2GB VPS during 4 months for free.