Waybar can be used as a status bar for SwayWM. In order to use it, you tell Sway to use it with (e.g. .config/sway/config):

bar {
    swaybar_command waybar
}

Configure waybar itself in ~/.config/waybar/config:

{
    "layer": "top",
    "modules-left": ["sway/workspaces", "sway/mode"],
    "modules-center": ["sway/window"],
    "modules-right": ["clock"],
    "sway/window": {
        "max-length": 50
    },
    "clock": {
        "format-alt": "{:%a, %d. %b  %H:%M}"
    }
}