I’ve made a list of the best free VPN trial I could find. Note that I’ve only included reliable VPN providers that I recommend.
Apparently, PureVPN and VyprVPN offer free trials, but make it difficult to get your money back, so you may want to avoid those services.
The ProtonVPN service is run by the people behind Protonmail. They offer a full free VPN account. However, the speeds of the free accounts are described as “medium”. The free plan is limited to three server locations — United States, Netherlands, and Japan. You get one simultaneous connection on the tree plan.