Even though the registration process has been improved significantly and can now be completed in a much shorter time than before, it will still take you a few minutes.
This would only give you a few rounds of play and a registration on the site wouldn’t really be worth the trouble. The amount would be used up too quickly, as many slots have a minimum bet of 20 cents or more. As long as you don’t plan on making use of a bonus offer, a €1 deposit usually doesn’t make a whole lot of sense.