Its better to have some weights, such as dumbells. But there are a lot of good body weight exercises. You can do push ups with you feet up on a chair or a stability ball. Split squats and lunges. If you do bulgarian split squats (rest the back leg on a bench or chair so more weight is on the front) you can hit the legs pretty hard.) A gallon water jug in each hand, or a brick or smaller paving stone will add some weight.
There are ways to improvise. If you have a pick up truck, you can do "step ups" right on the tires, swinging your self up and into the truck. Or grab the water jugs and go up a stadium stair, or other stairway.
The toughest things are you really can't do rows very easy without a bar. If you can find a bar low enough with room under it --maybe at a play ground--you can do bodweight rows by hanging underneat the bar and rowing your self up to it. The more level your feet and hand the harder it is to pull yourself up.