Specify on the can where fundraising donations will specifically go. Example: "To help Veterans". This helps those donating feel like they can associate their donation with an ongoing program, and if it happens to be one that warms their heart, they'll be more likely to give!
There are several commercial companies who sell fundraising donation containers in different materials and styles. They look "nicer" but reduce your profits. However, the printed labels can help 'legitimize' your drive. People tend to believe printed labels mean what they say.