Shinydashboard dashboardSidebar Width Setting

The width of the sidebar is set by CSS on the .left-side class, so you could do:

dashboardPage(
  dashboardHeader(title = "My Dashboard"),
  dashboardSidebar( tags$style(HTML("
      .main-sidebar{
        width: 300px;
      }
    ")),selectInput("id","Select a survey",choices=c("Very very very very long text","text"))), 
    dashboardBody()
  )

The old answer might still work, but there is also a width = ... option now. See: https://rstudio.github.io/shinydashboard/appearance.html#sidebar-width. Here is the example code shown over there:

shinyApp(
  ui = dashboardPage(
    dashboardHeader(
      title = "Title and sidebar 350 pixels wide",
      titleWidth = 350
    ),
    dashboardSidebar(
      width = 350,
      sidebarMenu(
        menuItem("Menu Item")
      )
    ),
    dashboardBody()
  ),
  server = function(input, output) { }
)