Lead-tin solder is generally melted by applying heat directly to the alloy. For a one liter can of alcohol, you should follow the steps below:
Prepare the area of the can to be welded, making sure it is clean and free of any debris.

Apply a flux to the area to be welded. The flux helps clean the surface and allows the solder to adhere properly.
Heat the lead-tin solder with a soldering iron until it melts. Tin-lead alloy has a low melting point, specifically 183°C for a 62/38 tin/lead alloy and 232°C for pure tin.

Apply the molten solder to the prepared area of the can, making sure that it adheres properly and forms a solid joint.
It is important to note that lead solder can be hazardous if ingested or inhaled, so handle with care and wear appropriate protective equipment. In addition, any container that has been soldered with lead should not be used to store food or beverages.